Lens for signal lights



Oct. 6', 1959 H. U. HJERMSTAD 2,907,249

LENS FOR SIGNAL LIGHTS Filed oct. 5. 195e @aA/7%- m p r l LENS non SIGNAL LIGHTS Hans U. Hjermstad, Chicago, Ill., assignor to Electro- Sielsal Corporation, Des Plaines, lll., a corporation of mois Application October S, 1956, Serial No. 614,111 8 Claims. (Cl. 88-78) The present invention relates to traffic controlsignals and particularly to light transmission lenses for the signal lights thereof.

In tr-aic control signals employing signal lights having colored lenses, one continuing and dangerous problem that arises in their use is that of phantom signals, that is, the condition that occurs when a signal lightwhich is not illuminated is made to appear illuminated by exterior light rays reected from the light. The condition occurs most commonly in the early morning or late afternoon when sunlight falls directly on the lens of a signal light, is transmitted therethrough, and is retiected back through the lens to an observer so as to cause the signal light to appear illuminated. Though this phenomena is experienced most commonly in sunlight under the conditions described, it may be caused by other light sources as well. irrespective of the light sources, the phantom signals produced constitute a continuous and serious threat to the safety of those depending upon traffic control provided by the signal lights, particularly where there are multiple signal lights such as stop, caution and go lights as inv the conventional traflic control systems. u

Accordingly, it is a general object of the present invention to provide an improved lens for signal lights that` prevents the occurrence of phantom signals.

A more specific object of the invention is to provide an improved lens for a signal light which displays a signal indication when the signal light is illuminated and displays another distinctive appearance when the signal light is not illuminated. v I

A further object of the invention is to provide an improved lens for a signal light which displays a mirrorlike appearance when the signal light is not illuminated and a signal indication when the signal light is illuminated.

Another object of the invention is to provide an improved lens fora signal light which carries on the one face thereof exposed to View a fragmentary mirror for displaying a mirror-like appearance when the signal light is not illuminated and for transmitting through the discontinuous portions of the mirror a signal indication when the signal light is illuminated.`

Another' object of the invention is to provide an improved lens for -a signallight which carries on its youter exposed face a fragmentary mirror of uniform configuration and which is formed on its inner face with a plurality of optical surfaces cooperatively positioned with re-v gard to the mirror portions carried on the outer face.` The fragmentary mirror on the outer face of the lens is arranged to cause the signal light to display a mirror-like appearance when the light is not illuminated and the optical surfaces on'the inner face are shaped and positioned with regard to the mirror portions so that when the light is illuminated, the light rays incident upon the inner face yof the lens are collected and projected through the lens and the discontinuous portions 'of the mirror, thereby' to `render a signal indication of an intensity that is com'- mensurate with the illumination provided by the signal light at the inner face rof the lens and substantially un- States Patent 1;..

diminished by the fragmentary mirror portions on the outer face.

Further features of the invention pertain to the particular configuration of the improved lens for the signal light, whereby the above-outlined and -additional operating features thereof are attained.

The invention both as to its organization and method of operation, together with further objects and advantages thereof, will be best understood by reference to the following specification taken in conjunction With the accompanying drawing, in which:

Figure 1 is a plan view of a signal light embodying the lens structure of the invention;

Fig. 2 is a vertical sectional-view taken on line 2-2 ofFig.l; I

Fig. 2A is a detailed vertical sectional-view of a portion of the lens structure of Fig. 2; y

Fig. 3 is la detailed horizontal sectional-view of a portion of the lens structure taken along the line 3-3 of Fig. l.

Referring to the drawings, there is shown in Figs.v l and Zan operatively controlled signal light 10, in accordance with the invention, including a colored light transmission iens 11, a reflector 12, a light source 13, and a lighting circuit including a source of potential 14 and a switch 15. The lens 11 carries on its exposed outer face 16 a fragment-ary mirror 17, as is best shown in Fig. l, and is formed on its inner face 18 of a plurality of optical surfaces 19, as is best shown in thecross-sectional view of Fig. 2. The reflector 12 is preferably a parabolic Asurface wherein the lighting element of the light source 18 of the signal lens 11. The parallel light rays 20 impingent upon the face 18 of the lens 11 are refracted in the lens in accordance with the configuration of the optical surfaces 19 forming the innerface 18 of the lensll and are transmitted through the lens and projected from the outer face 16 atthe areas v21,A formed by the discontin nous portions of theA fragmentary mirror 17, in a direction normally intercepted by aperson viewing the signal light. When the light source 13 is not illuminated by the switch 15 being open, no light is projected from theiareas .21.

on the face 16 of the lens 11 but the fragmentary mirror 17 on the face 16 responds to the exterior light rays 22 incident upon the'outer face 16 by reecting the light rays from the face 16 in adirection towards the source thereof and in the direction normally intercepted by a person'viewing the signal light, as shown inV Fig. 2. Accordingly, the signal light presents to a person viewing the same a high intensity signal indication characterized bythe particularcolor of the lens 1.1 when the signal light is illuminated from theV interior and a mirror-like appearancecharacteristic of the exterior incident light rays as modulated by the color of the fragmentary mirror 17 when the signal light is not illuminatedfrom the interior. p

Considering now, in greater detail, the composition of the lens 11, the material of which the lens is made must be of high efficiency lighttransmission material and is conventionally of glass, but may also be plastic, and is of a coloi to provide a signal indication when illuminated. Further, the lens is conventionally' of a substantially uniformthiclmessA and is in the general shape ofv a spheric section, as showu in Fig.v 2, though infact neither of these conditions is critical to the practice of the present invention.

With regard to the configuration of the lens in accord-i' ance with the invention, and referring specifically to the detaile'dvertical cross-sectional'view of Fig 2A and the detailed horizontal cross-sectional view of Fig. 3, the optical surfaces 1,9: form, preferably though not nec ess'arily, theenti'resurface of the inner face 18, are con-l vex in shape, and are generally surfaces of revolution characterized refracting light incident thereupon to,- w'ards the' centers of revolution andq may, for example, take 'the specific form of a spheric, spheroidic, cylindric, conic, or toric lens sections) Thi? Qptical sur-faces 19 may be formed on the "inner face 'sof that the optica'laxis of each is perpendicular to the general spheric curvature of the lens' but'preferably,`and as shown in Fig. 2, the optical surfaces'19, are formed onl the inner face so' that the optical axis of each-'is parallel to the longitudinal axis of the lens,"wh e`rehyl there is a greater concentration of the light refracted` by the, optical surfaces and'pr'ojected through the'ext areas Z1.

Additionally, it may be desirable tov modify the general shape of the convex optical surface chosen'in a, manner as` shown in Fig. 3 wherein each of the optical surfaces 1,9illustrated is of the general form of a cylindric Ycurved atits extreme end portions to refract the light incident thereupon not only towards the center iine'of revolutionV (not shown) butI also to refractthe, light incident on the curved end portions towards the lateral center of the center line of revolution.V Accordingly, substantially all of the`L parallel light beams Z0` directed towardsy the inner face 18,- of the lens impingeY upon the optical surfaces 19'and at each optical surfacev 1.94 the impinging light rays are refracted in the lens towards theV lgeornetriccenter of the optical surface; wherel` by substantially all ofthe light ux entered upon the inner face 18is collected at the optical surfaces 19, concentrated by refraction from the outer vface 1,6 spending to each of the. ner asdetermined by the ofthe lens. at areas 21 corref optical surfaces 19, in a man-v radius of curvature of the se: lectedbptical surface 19, the index refraction of the; lens material, and the thickness of the lens. At the. areas 21z the light projectedtherefrom is again retracted into the viewing area.v i A A Y' Y l The fragmentary mirror 17r cari-leden the outer, or. ont, face 16 of thezlens 11k is discontinuous at the prot-'1` jection areas 21 on the outer 'face` and is comprised, in fact, lof, a plurality of;A reflective'lislands,positioned exfl teriorto theprojectionareas 21A. or, vasl shownin Fig. l, of a plurality of intersecting bands' of reflective materialg positionedbetween the projection areas, 21. The par-.. ticular configurationzchosen for the `fragnlentary mirror4 is determined essentially by thelconiiguration taken by.A the projection areasl 21, andas theprojection areas 2 1, form a patternon the outer:fac e, thefragmentary mirf nor 1 7 formsa complementaryA pattern covering the non,l projection areas of the outer fac :e,1r6.y The reflective mag terial forming the fragmentary mirror f may be kof any number of reflective materials in commontuse, .suchwasj aluminum, stainless steel, chromium, silver, copper, gold, etc., andmay lbe applied to the surfacewof the face 16,- by electro-plating orchemicaldeposition, or by painting by means oflza brush or spray,- sputten'ng, orevaporating,` through a Screen- The reetive material `S0 applied may be of athicknessvsoas to permit transmission therethrough of 'the light normally diffused in the lens and` thereby add to the brilliance ofthe signal indication when the signal light is illuminated, or the reflected ula-v terial may/ beef a Ythixclme'ss soas toA :render the covered areas of the face 16, substantially opaque, At the present, timethe Vlatter arrangementUiS-preferred yforreasons of; production` control and becauseithe ,intensity of; the diffused light available inl the` lens for transmission@ through the reetivecoatings is .slightas compared to.- the mtensityvof the iight `v projected` from the lareas 21a and-when transmitted through a thinflilrn ofthe re. EllYmttil adda.nlyimnerceptihlyto thabrlliance within thek lens and projectedf of the Asignal indication. An additional advantage to making the fragmentary mirror opaque is that any exterior light incident upon the outer face 16 of the lens and entered into the signal light through the exist areas 21 and reflected therein is prevented by the opaqueness of the mirror from rendering a phantom signal display as to that area of the lens covered by the fragmentary mirror.

The surfaces of the projection areas 21 on the face 1,6 of the lens may conform to the general curvature of the lens face whereby the light rays projected from the areas 21 are substantially diiused. This arrangement is considered to be preferred inasmuch as the light rays projected therefrom provides a brilliant display to a person viewing the light at a position in alignment with the light and remote therefrom and also provide a clear display to a person viewing the light at a position oblique to the light and` in close proximity thereto so that the Signal light is well suited. fer,- directing automotive trafc as well as pedestrian traffic.

Alternatively, the surface. of each, ofthe projection areas 2 1 may be convex in shape and either protruded. from or recessedv in the lens face whereby the light rays Projected from the areas. are further diffused tcprof vide a display of greater` brilliance to persons viewing the signal light` at a positionVv oblique to the light and in c lose proximity thereto and without destroying theY effectiveness of the signalfor directing-the normally more remotely positioned automotive` trac. rI *he convex Shape of the projection areastmay be spheric, spheroidic, etc., as .previously outlined, depending upon the diffusion-j pattern desired and considered to be most appropriatev fof .the use intended;

Additionally, the `surface ofeach of the projection areas 2,11nayL be concave in shape and either recessedl in,the,lens face orrpositioned llush with the curvature thereof4 whereby the light raysprojected from the areas, 21; are`- retracted towardsthe centerl of, revolution thereof and are concentratedtoprovide a display of. greaterV brilliance to persons viewing the signal light at a position in ,alignment therewith andgrernote therefromand without,` destroyingA the, effectiveness of. the signalV for, directing; the normally more closelyV and obliquelypositioned pedestrianl traffic. The concave shape of the projections areas Z1 maybe spheric, spherodic, etc.as previously outlined, dependingv uponthe concentrationpattern desired. For example, assuming that the optical surfaces 19; aremodiied toricsections ,for which the optical-axes are parallelto the longitudinal axis ofthe lens, as shown in. Figs.` 2A- and 3, should it be desired to provide a substantiallyparallel array of projected lightV beams such, as `would be suitable for use in railway or highway trafvfic control the projection areas 21 may be concave surfaces offrevolution substantially,identical in form to thoseY of the optical surfaces19, thatis, modiiedtoric sections, hayingthe same centers of'revolutionandhaving opticalaxes common tolthose of the. correspondingfop-v.

l 4tical surfaces 19.

With; regards to the relative areas occupied bythe fragmentary mirrorl? and thev projection areas 21 on the` outer facev 16 ofthe, lens `1,1, it-is to beV appreciated lthatt thearrangernents ofthe areas shownV in Athe drawings is meant to `be schematic for the purpose of more easily illustratingthe invention. Thoughithe range ofeffective relative areasisquite broad,v itV has .been determinedthat themostecient transmission and reflection results areg obtainedv iffthej fragmentary mirror comprises approxi-r.y lofthe, surface kareaV ofthe face 16. Additionally, it is preferable that the projection areas be close-V lyspaced4 soasto present the appearance. of a continuous light source toV an `observer ,atra ,critical signal distance.v Specically, andassuming. that, a viewing,position 50/` feetnfrom the signal lightisvconsidered .to .be acritical signaldistance, the humaneye. has azresolving powerL of approximately one part in3,438bso thatltoa viewer.

presented to a viewer '-at the distance of 50 feet from a signallight the projec- 'ition areas will be unresolved and the lens will appear 'uniformly illuminated when the yprojection areas are spaced no further apart than' '0K6 of an inch, which means ithat the band of reflective materials shown inPig. 1 going to make up the fragmentary mirror 17 should be ino wider than 3716 of an inch.

In view of the foregoing, it is apparent thatthere has ibeen provided a lens for a signal light of improved construction and arrangement sopthat when the signal light is illuminated a high intensity signal indication is provided to a 'viewer of the signal light, 'and when the signal light is not illuminated la distinctive mirror-light appearance is of the signal light.

While there has been described what is at present considered to be preferred embodiment of the invention, it'will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A light transmission optic for an operatively controlled signal light comprising a single element lens of light-transmitting material having a back face and a front face and being formed on the back face thereof in a plurality of optical surfaces and carrying on the front face thereof a fragmentary mirror, each of said optical surfaces having an individually associated optical axis and being shaped so as to refract light incident upon the surface thereof and converge said refracted light towards said optical axis, said fragmentary mirror consisting essentially of a layer of reflective material having therein a plurality of discontinuities corresponding to said optical surfaces whereof said discontinuities are centered with regard to said optical axes, said lens being characterized by the transmission of substantially all of the light incident upon the back face thereof and by the reflection of a substantial portion of the light incident upon the front face thereof, so that said lens when positioned in a signal light with the front face exposed to view presents to a person viewing the same a mirror-like appearance when the signal light is not illuminated and a signal indication when the signal light is illuminated.

2. A light transmission optic for an operatively controlled signal light comprising a single element lens of light-transmitting material having front face and being formed on the back face thereof in a back face and a a plurality of symmetric optical surfaces and carrying on the front face thereof a fragmentary mirror, each of said optical surfaces having an individually associated optical axis and being shaped so as to refract light entering upon the area of the surface thereof` towards said optical axis and to project said refracted light through the front face of said lens at a corresponding exit area that is small as compared to the entrance area, said fragmentary mirror consisting essentially of an apertured layer of reflective material arranged on the front face of said lens with the apertures in said layer coincident with said exit areas, said lens being characterized by the transmission of substantially all of the light incident upon the back face thereof and by the reflection of a substantial portion of the light incident upon the front face thereof, so that said lens when positioned in a signal light with the front face exposed to view presents to a person viewing the same a mirror-like appearance when the signal light is not illuminated and a signal indication when the signal light is illuminated.

3. A light transmission optic for an operatively con! trolled signal light comprising a single element spherical section lens of light-transmitting material having an inner face and an outer face and being formed on the faces thereof in a plurality of optical surfaces and carrying on the outer face thereof a fragmentary mirror, each of the optical surfaces on said inner face having an individually associated optical axis and being a convex surface of revolution shaped so as to refractA light. entering upon the area of the surface thereof towards said optical `axis and to project said refracted light through the outer face of said lens at a corresponding exit area that is small as compared tothe entrance area, each of the optical surfaces on said outer face corresponding to a one of said optical surfaces on said inner-,face and being laterally coextensive withv the corresponding exit area, said fragmentaryY mirror being composed of a layer of reflective material covering only thatY arearofsaid outer face lying between said optical surfaces thereon, said lens I.being characterized by the transmission of substantially all of the light incident upon the inner face thereof and by the reflection of asubstantial portion of the light incident upon the outer face thereof, so that said lens when positioned in a signal light With` the louter face exposed to view A.presents to a person viewing the same: a mirrorlike appearance when the signal light is not illuminated and a signal indication when the signal light is illuminated.

4. The light transmission optic set forth in claim 3 wherein each of the optical surfaces on said outer face conform to the spheric curvature of the outer face of said lens.

5. A light transmission optic for an operatively controlled signal light comprising a single element spherical section lens of light-transmitting material having an inner face and an outer face, said lens at said inner face being formed over substantially the entire area thereof in a plurality of first optical surfaces each having an optical axis associated therewith, each of said first optical surfaces being a convex surface of revolution shaped so as to refract light entering upon the area of the surface thereof towards said optical axis and to project said refracted light through the outer face of said lens at an exit area that is small as compared to the entrance area, said lens at said outer face being formed at the exit areas thereon in a corresponding plurality of second optical surfaces and being formed over that area thereof between said second optical surfaces in a fragmentary mirror, whereby said lens is characterized by the transmission at the second optical surfaces on said outer face of substantially all of the light incident upon the inner face thereof and by Ethe reflection at said fragmentary mirror on said outer face of a substantial portion of the light incident upon the outer face thereof, so that said lens when positioned in a signal light with the outer face exposed to view presents rto a person viewing the same a mirror-like appearance when the signal light is not illuminated and a signal indication when the signal light is illuminated.

6. The light transmission optic set forth in claim 5 wherein said fragmentary mirror consists essentially of an opaque layer of reflective material so that substantially all of the light incident upon said fragmentary mirror is reflected therefrom.

7. The light transmission optic set forth 'in claim 5 wherein said fragmentary mirror constitutes essentially of a translucent layer of reflective material so as to reflect a portion of the light incident on the fragmentary mirror and so as to transmit therethrough a portion of the light normally diffused in the lens thereof when the signal light is illuminated.

8. A light transmission optic for an operatively controlled signal light comprising a single element spherical section lens of light-transmitting material having an inner face and an outer face, said lens at said inner face Vbeing formed over substantially the entire areathereof in a plurality of first Yoptical surfaces eachvhaving an optical axis associated therewith parallel to the longitudinal axis of said lens, each of said first optical surfaces. being a convex surface of revolution `shaped so as toV refract light entering upon the area of the surface thereof towards said optical axis and to project said refracted light through the outer face of said lens at an exit area that is small ab compared to said area upon which said retracted light enters, said lens at said outer face being formed at the exit areasv thereon in a corresponding plurality of second optical surfaces and being formed over that area thereof between said second optical surV faces in a fragmentary mirror, each of said second optical surfaces conforming to thespheric curvature of the outer face of said lens, and said fragmentary mirror consisting essentially of an opaque layer of reflective material, whereby said lens is characterized by the transmission at the second optical surfaces on said outer face of substantially all of the light` incident upon the inner face thereof vand bythe reection at said fragmentary mirror on said outer facerf a substantial port-ion of the light incident upon the outer face thereof, so that said lens when positioned in a signal light with the outer face exposed to View presents to -a person viewing the same a mirror-like appearance when the signal light is not illumnated and a'signal'indication when the signal light is illuminated.

' semences. ci@ in un me, .or his pas@ UNITEDJ STATES. PATEIrIrSQ` 

